Seaming process for pmc fabric having monofilament yarns

ABSTRACT

A seaming process for a PMC fabric includes the steps of: providing a PMC fabric including a plurality of monofilament yarns, at least some of the monofilament yarns having a composition including between approximately 100 to 10,000 parts per million (ppm) of an additive to improve yarn visibility for the fringed ends of an illuminated PMC fabric.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to paper machine clothing, and more particularly, to seaming processes used to join ends of the clothing in an endless manner.

2. Description of the Related Art

A paper machine clothing (PMC) fabric is typically manufactured with a specific set of design and quality specifications for a particular paper machine's performance requirements. These specifications include surface characteristics, open area, void volume, permeability and smoothness, among others.

Flat woven PMC fabrics are seamed after heat setting to form an endless belt. Seaming is the most time-consuming, costly and tedious part of PMC fabric manufacturing. Weft yarns are raveled out on both ends of the fabric, creating a warp fringe. Warp yarns on both ends of the fabric are then woven together one by one using filling yarn. There are many ways of joining the warp ends together to achieve a desired seam strength. Depending on the strength requirements, the seamed area of the PMC fabric can be several inches long.

After seaming, the PMC fabric is given a final heat set to relieve the stresses in the seaming area. The final heat setting temperature is lower than the preliminary heat setting temperature in order not to alter the properties of the PMC fabric that were set during preliminary heat set. After final heat setting, the fabric edges are trimmed to the paper machine width.

During the seaming process, it is common for much of the weaving to be done by hand. It can be difficult for a person to see the individual yarns such as the exposed warp yarns in the fringe area. When the PMC fabric yarn is composed of darker colored or fine diameter yarns, e.g., fine diameter yarns below 0.25 mm, the exposed warp yarns in the fringe area can be even more difficult to see with the human eye. This compounds the difficulty and expense of the seaming process.

What is needed in the art is a seaming process for a PMC fabric which allows the fringe ends to be more easily woven together.

SUMMARY OF THE INVENTION

The present invention provides a monofilament yarn for a PMC fabric with an additive that makes the yarn ends easily visible using a light or radiation source. The mechanical properties of the monofilament yarn are not altered by the addition of the additive.

The present invention in one form is directed to a seaming process for a PMC fabric, including the steps of: providing a PMC fabric including a plurality of monofilament yarns, at least some of the monofilament yarns having a composition including between approximately 100 to 10,000 parts per million (ppm) of an additive to improve yarn visibility for the fringed ends of an illuminated PMC fabric.

An advantage of the present invention is that the fringed ends of the fabric can be easily seen under a light or radiation source by a person during the seaming process.

Another advantage of the present invention is that the addition of the additive does not substantially alter the physical properties of the monofilament yarn.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a fragmentary, perspective view of a portion of a fabric including an embodiment of a monofilament yarn of the present invention;

FIG. 2 is an illustration of absorption and emission spectra;

FIG. 3 is an illustration of the principle of fluorescence;

FIG. 4 is a schematic view of a portion of a fabric with the fringed end being illuminated with a UV light;

FIG. 5 is a flow chart illustrating an embodiment of the method of making monofilament yarns according to the present invention;

FIG. 6 is a flow chart illustrating an embodiment of the seaming process for a PMC fabric according to the present invention; and

FIG. 7 is a flow chart illustrating another embodiment of the method of making monofilament yarns according to the present invention;

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there is shown a portion of an embodiment of a PMC fabric 10 including a plurality of woven monofilament yarns, namely warp yarns 12A extending in the running or machine direction, and weft yarns 12B extending in the cross-machine direction. The specific configuration of fabric 10 may vary, depending upon the application. For example, the specific weave pattern of fabric 10 may vary from one application to another.

The composition of the monofilament yarns 12A and 12B include an additive and a thermoplastic resin. In order to more easily see the individual yarns of the PMC fabric during a seaming process, an additive is added during the monofilament yarn making process. This additive makes the yarn easily visible.

More specifically, PMC fabric 10 is formed from a plurality of monofilament yarns 12, for example woven yarns, including an additive, for example a UV additive manufactured by Eastman Chemicals as Eastobrite OB-1™, loading of between approximately 100 to 10,000 parts per million (ppm), for example 1,000 ppm, which makes the fringe at opposite ends of PMC fabric 10 easily visible under black light (which generally emits radiation at wavelengths between approximately 350 nm and 390 nm) while weaving the fringe during a seaming process. The inclusion of an additive is especially useful for fine diameter yarns (below 0.25 mm) and dark colored monofilament yarns (L* value less than 50) which are harder to see with the human eye. A color measurement system, such as CIE L*a*b* or the Yellowness index, can be used to quantify the darkness of the yarn.

A UV additive, also known as an optical brightener (OB) or fluorescent whitening agent absorbs the short wavelength electromagnetic radiation from a radiation source, such as a black light having a wavelength e.g., between approximately 300 nm and 400 nm, which is invisible to the human eye and converts it into visible light of a longer wavelength, for example between approximately 400 nm and 500 nm, which is emitted either as violet, blue or greenish blue light. This principle is generally illustrated in FIG. 2, which illustrates absorption 14 and emission 16 spectra as they relate to energy and wavelength.

Fluorescent whitening agents are compounds that are excited or activated by wavelengths in the near-UV range, for example having a wavelength between approximately 360 nm and 365 nm, and then emit light in the blue range, for example having a wavelength between approximately 400 nm and 440 nm. Electrons in fluorescent molecules are excited into a higher energy state by absorption of light, which then emit a small amount of heat plus fluorescence as the electrons return to their ground state. FIG. 3 illustrates this general principle via the application of wavelengths of light 18 in the near-UV range, for example between approximately 360 nm and 365 nm, to a molecule of fluorescent whitening agent 20 which thereby activates the fluorescent whitening agent by exciting the electrons of the fluorescent molecules, raising them to a higher energy state 22 by absorption of light 18, which then results in the emission of a small amount of heat 24 and a second lower excited state 26 plus fluorescence 28 as the electrons of the fluorescent molecules return to their ground state 30, which is the lowest energy state of the molecule.

FIG. 4 illustrates a schematic view of a portion of a PMC fabric 10 with the fringed end being illuminated with a radiation source in the form of a UV light 13. It will be appreciated that to make a PMC fabric 10 endless, opposite ends of the PMC fabric 10 are fringed to define a fringe area F with exposed warp yarns 12A of a predetermined length. Only one end of PMC fabric 10 with a fringed area F is shown in FIG. 4 for simplicity sake, the opposite fringed end being substantially identical. At least the warp yarns 12A include the UV additive to be easily visible during the seaming process; however, weft yarns 12B may also include the UV additive. The fringed warp yarns 12A of the adjacent fringed ends are woven together during the seaming process to define a seam and thereby make PMC fabric 10 endless.

Example 1

A sample PET monofilament yarn without a UV additive was compared with a PET monofilament yarn including a UV additive. Table 1 shows some of the physical properties of the PET monofilament used for a PMC Dryer Fabric. The control sample (with no UV additive) is shown in the first column and the properties of the yarn with the UV additive, 1000 ppm loading, are shown in the second column. Table 1 shows that the physical properties of the yarn with the UV additive are substantially the same as the PET monofilament without the UV additive. Therefore, it is clear that the UV additive according to the present invention does not substantially alter the physical characteristics of the monofilament yarn.

TABLE 1 PET Dryer Yarn Comparison (with and without UV Additive) With With Additive Additive PET PET PET PET 0.40 mm 0.40 mm 0.33 mm 0.33 mm Denier (g/9000 m) 1560 1565 1066 1060 TEX (g/1000 m) 173 174 118 118 Tenacity (g/den) 5.8 5.9 5.9 5.8 Tenacity (cN/tex) 51.2 52.1 52.1 51.2 Modulus (g/den) 75 75 79.4 80 Modulus (cN/tex) 662 662 701 706 Elongation (%) 17.7 17.8 18 17 Loop Strength (lbs) 15.5 15.6 11.4 11.1 Loop Strength (N) 69.0 69.5 50.8 49.4 Knot Strength (lbs) 9.4 9.2 7.7 7.8 Knot Strength (N) 41.9 41.0 34.3 34.7 Shrink Force (g) 317 320 203 200 Shrink Force (cN/tex) 1.79 1.80 1.68 1.67 T@Max Shrink 170 171 170 169 Force (C.) Shrinkage 8.5 8.6 6.7 6.5 (140 C., 3 min) (%)

TABLE 2 Range of L * values based on CIE L * a * b * test Yarn color method Red 37.9-43.6 Blue 34.9-40.8 Black 17.0-17.1

During the manufacture of PMC fabric 10, a screw extruder is used to melt blend a mixture of thermoplastic resin (preferably PET) and a UV additive, for example a stilbene. (FIG. 4, block 32). The mixture is then spun into a filament (block 34). The filament is then subsequently drawn into a monofilament PMC fabric yarn with at least one predetermined physical property (block 36). The PMC fabric yarn is then woven into PMC fabric 10.

During a seaming process of the present invention, a PMC fabric is provided which includes a plurality of monofilament yarns, at least some of which include between approximately 100 ppm to 4,000 ppm of a UV additive. (FIG. 6, block 38). Opposite ends of the PMC fabric are fringed by removing filling yarns at the respective opposite ends (block 40). The fringed ends of the PMC fabric are illuminated using short wavelength radiation at a wavelength of between approximately 300 nm to 400 nm (block 42). The fringed ends of the illuminated PMC fabric are woven together to complete the seam (block 44).

During the manufacture of another embodiment of PMC fabric 10, the additive is coated on the yarns rather than incorporated into the composition of the yarns. To that end, a thermoplastic resin (preferably PET) is spun into a filament (FIG. 7, block 46). The filament is then drawn and subsequently coated with an additive which improves the yarn visibility (blocks 48 and 50). The PMC fabric yarn may then be woven into PMC fabric 10.

While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims. 

1. A seaming process for a paper machine clothing (PMC) fabric, the seaming process comprising the steps of: providing a PMC fabric including a plurality of monofilament yarns, at least some of said monofilament yarns having a composition including an additive to improve yarn visibility; fringing opposite ends of the PMC fabric by removing filling yarns at the respective opposite ends; illuminating the fringed ends of the PMC fabric; and weaving together the fringed ends of the illuminated PMC fabric.
 2. The seaming process for a PMC fabric according to claim 1, wherein the additive is at least one of a UV additive, an IR additive, and a metal powder additive.
 3. The seaming process for a PMC fabric according to claim 1, wherein said plurality of monofilament yarns include a plurality of warp yarns and a plurality of weft yarns, and all of said warp yarns include said additive.
 4. The seaming process for a PMC fabric according to claim 1, wherein at least some of said monofilament yarns include between approximately 100 to 10,000 parts per million (ppm) of an additive.
 5. The seaming process for a PMC fabric according to claim 4, wherein at least some of said monofilament yarns include approximately 1,000 ppm loading of said additive.
 6. The seaming process for a PMC fabric according to claim 1, wherein the fringed ends of the PMC fabric are illuminated using radiation at a wavelength to make the additive visible.
 7. The seaming process for a PMC fabric according to claim 1, wherein said additive is a stilbene.
 8. The seaming process for a PMC fabric according to claim 7, wherein said stilbene is 4,4′-bis (benzoxazol) stilbene.
 9. The seaming process for a PMC fabric according to claim 1, wherein said PMC fabric includes a plurality of woven yarns.
 10. The seaming process for a PMC fabric yarn according to claim 1, wherein said composition further comprises a thermoplastic resin.
 11. The seaming process for a PMC fabric yarn according to claim 10, wherein said thermoplastic resin is polyethylene terephthalate (PET).
 12. The seaming process for a PMC fabric yarn according to claim 11, wherein said composition has a tenacity which is approximately the same as said PET alone.
 13. The seaming process for a PMC fabric yarn according to claim 11, wherein said composition has a relative elongation which is approximately the same as said PET alone.
 14. The seaming process for a PMC fabric yarn according to claim 11, wherein said composition has a loop strength which is approximately the same as said PET alone.
 15. A seaming process for a paper machine clothing (PMC) fabric, the seaming process comprising the steps of: providing a PMC fabric including a plurality of monofilament yarns, at least some of said monofilament yarns being coated with a coating formulation which includes an additive to improve yarn visibility; fringing opposite ends of the PMC fabric by removing filling yarns at the respective opposite ends; illuminating the fringed ends of the PMC fabric; and weaving together the fringed ends of the illuminated PMC fabric.
 16. The seaming process for a PMC fabric according to claim 15, wherein the additive is at least one of a UV additive, an IR additive, and a metal powder additive.
 17. The seaming process for a PMC fabric according to claim 15, wherein said plurality of monofilament yarns include a plurality of warp yarns and a plurality of weft yarns, and all of said warp yarns include said additive.
 18. The seaming process for a PMC fabric according to claim 15, wherein at least some of said monofilament yarns include between approximately 100 to 10,000 parts per million (ppm) of an additive.
 19. The seaming process for a PMC fabric according to claim 18, wherein at least some of said monofilament yarns include approximately 1,000 ppm loading of said additive.
 20. The seaming process for a PMC fabric according to claim 15, wherein the fringed ends of the PMC fabric are illuminated using radiation at a wavelength to make the additive visible.
 21. The seaming process for a PMC fabric according to claim 15, wherein said additive is a stilbene.
 22. The seaming process for a PMC fabric according to claim 21, wherein said stilbene is 4,4′-bis (benzoxazol) stilbene.
 23. The seaming process for a PMC fabric according to claim 15, wherein said PMC fabric includes a plurality of woven yarns.
 24. The seaming process for a PMC fabric yarn according to claim 15, wherein said composition further comprises a thermoplastic resin.
 25. The seaming process for a PMC fabric yarn according to claim 24, wherein said thermoplastic resin is polyethylene terephthalate (PET).
 26. The seaming process for a PMC fabric yarn according to claim 25, wherein said composition has a tenacity which is approximately the same as said PET alone.
 27. The seaming process for a PMC fabric yarn according to claim 25, wherein said composition has a relative elongation which is approximately the same as said PET alone.
 28. The seaming process for a PMC fabric yarn according to claim 25, wherein said composition has a loop strength which is approximately the same as said PET alone. 